1. Field of the Invention
The present invention relates to a driving system for a rotary press.
2. Description of the Prior Art
Description first will be made of a prior art driving system for a rotary press, art with reference to FIGS. 8 and 9. The known driving system for a rotary press is illustrated generally in FIG. 8, and a plate clamping device of a plate drum used in the known rotary press is shown in cross-section in FIG. 9. In FIG. 8, reference numerals 01, 02 and 03 respectively designate printing units of the known rotary press, and numeral 04 designates a folding machine thereof. In this rotary press, a main shaft 05 consists of main shaft sections connected in series along a straight line via a plurality of couplings 06 over the entire length of the rotary press so that it can be rotated synchronously. Also, for each of the printing units is formed a drive unit 010 which can rotate plate drums 09 and 09' in each printing unit in forward or reverse directions at a very slow speed (about 10 rpm) by means of an individual drive motor 08 by disconnecting a clutch 07. (In FIG. 8, the respective drive units 010 are enclosed by respective double-dot chain lines.) Reference numerals 011 designate branch shafts branched via bevel gear boxes 012, and numerals 013 designate electromagnetic brakes.
In FIG. 9, a plate clamping device 014 is provided for the purpose of stretching and securing a plate 015 onto the drum circumference of the plate drum 09. Clamping and dismounting of the plate 015 is effected by means of this device, and upon performing this operation it is necessary to stop the plate drum 09 at such location that manipulation of the plate clamping device 014 can be provided easily. To that end it is commonly effected that the drive unit 010 is isolated by disconnecting the clutch 07, the plate drum is made to rotate in a forward or reverse direction at a very slow speed of about 10 rpm by means of the individual drive motor 08, and when the plate clamping device 014 has come to a position where a mounting operation easily may be performed, the plate drums 09 and 09' are stopped by means of the electromagnetic brake 013 by manipulating a switch button. However, in many cases the plate drum will stop at a position considerably deviated from a desired stop position. Even if it is attempted to eliminate this disadvantage by stopping the plate drum by automatically actuating the electromagnetic brake by an approach sensor, the precision of the stop position will be on the order of .+-.10 mm relative to the circumferential surface of the plate drum due to fluctuations of load. This degree of precision is insufficient for use with recently developed automatic plate exchange systems.
Furthermore, since the clutches in the respective drive units are disconnected for exchanging the plates in the respective printing units, after completion of a plate mounting operation, phase matching of all of the respective printing units must be effected by connecting the respective clutches again at predetermined positions, and the deviation of the plate drum stop position in each printing unit is enlarged a deviation phase angle by approximately four fold at the main shaft due to the gear ratio involved. Therefore, methods employed in the prior art for attempting to avoid this problems include the following:
(1) Upon connecting a clutch, a mark on a wheel mounted on the main shaft is aligned with a mark on the opposite member by manually rotating the latter. Then the clutch is connected by means of a push-out device (by making use of an air cylinder or the like). Thereby, the clutch is connected at such position that a pin-shaped inter-unit phase-matching guide can enter into the opposite member.
(2) A clutch device having a wedge mechanism is used.
Though it is realized that the stop position of a plate drum must be achieved at a severe level of precision to make possible automation of the plate exchange operation, the above-described prior art system cannot satisfy this requirement, since the stop position will vary every time due to fluctuations of load, and the precision of stoppage is at a deviation of even .+-.10 mm on the circumference of the plate drum. In addition, since plate exchange is effected for each printing unit, it is carried out after a clutch in each drive unit has been disconnected. Thus, when the plate exchange operation has been finished, to enable synchronous operation again to be carried out, the clutches must be reconnected in a manner to bring the respective printing units into the same phase. However, in the above-described prior art system, the deviation of the stop position of each plate drum is enlarged at the main shaft, due to the gear ratio, to a deviation phase angle increased by about four fold. Hence, in a meshing type clutch which performs fixed position connection, coupling cannot be done and coupling is effected after phase matching has been carried out separately. Therefore, additional time and labor are necessitated. Furthermore, even if a correcting device having a wedge mechanism is employed for phase matching of the clutch, frictional resistance is large at the slide portion of the wedge, and thus, a large-sized device becomes necessary.